Effects Of Atmospheric Dust Research Articles

The effects of atmospheric dust and solar radiation on the dayside ionosphere of Mars derived from 17 years of Mars Express radio science observations

This work combines 17 years of Mars Express radio science (MaRS) observations with proxies for insolation and local/global atmospheric dust to investigate the combined and individual effects on the dayside ionosphere of Mars from the top down to the ionospheric base.The increase in insolation from orbital apocenter to pericenter in combination with Mars‘ dust cycle causes an average rise of the whole photochemically dominated region of the dayside ionosphere, ranging from 13 km at the ionospheric base up to 22 km above the main peak during conditions without a global dust storm. The declining phase of the 2018 global dust storm was observed by MaRS on the southern hemisphere and close to pericenter. The observed lifting effect on the whole photochemically dominated region of the ionosphere from the increased insolation and the high local and global atmospheric dust levels exceeds that seen by MaRS from similar seasons during years without a global dust storm.The average ionospheric peak altitude at the subsolar point rises for increasing levels of local atmospheric dust until a maximum elevation is reached. This maximum depends on the available insolation at the top of the planetary atmosphere. Further increases of the local atmospheric dust levels do not lead to a further rise of the average ionospheric peak altitude in the investigated data set. This indicates a limit for the warming/expansion of the lower neutral atmosphere and the consecutive lifting of the ionosphere based on the available insolation and explains why regional dust storms can cause a similar lifting of the ionospheric main peak region as global dust storms.

Evaluation of minerals being deposited in the Red Sea using gravimetric, size distribution, and mineralogical analysis of dust deposition samples collected along the Red Sea coastal plain

Abstract The effect of atmospheric dust on the Earth's climate and air quality is especially severe in the major dust-source regions of the globe, such as the Arabian Peninsula. To better quantify the impact of dust over this region, we established the dust deposition measurement sites at King Abdullah University of Science and Technology (KAUST) and an AErosol RObotic NETwork (AERONET) station. We measured and analyzed dust deposition for 61 months from 2014 to 2019, totaling 442 samples, in 6 different locations on the KAUST campus (22.3 N; 39.1E). The analyses include gravimetric measurements, X-Ray Diffraction (XRD) mineral analyses, and particle size distribution measurements. The intercomparisons of the samples collected from different sampling sites show that the dust deposition rates on campus are spatially uniform. Particle size and mass measurements of deposition dust samples are found to be uncorrelated with the concurrent AERONET measurements. Deposition sample sieving (D 20 µm are typically of local origin, since they deposit quickly. The annual mean deposition rate is about 11 g m-2 mo-1, with higher spring and fall rates and reduced rates in summer. The mineralogical analysis shows an abundance of quartz and feldspar with lesser amounts of micas, gypsum, clays, carbonate, halite, and iron oxides. Gypsum traces are probably produced either in the atmosphere or in the deposited sample by the reaction between carbonates and sulfur dioxide. The deposition of dust particles with D

Electrostatic forces alter particle size distributions in atmospheric dust

Abstract. Large amounts of dust are lofted into the atmosphere from arid regions of the world before being transported up to thousands of kilometers. This atmospheric dust interacts with solar radiation and causes changes in the climate, with larger-sized particles having a heating effect, and smaller-sized particles having a cooling effect. Previous studies on the long-range transport of dust have found larger particles than expected, without a model to explain their transport. Here, we investigate the effect of electric fields on lofted airborne dust by blowing sand through a vertically oriented electric field, and characterizing the size distribution as a function of height. We also model this system, considering the gravitational, drag, and electrostatic forces on particles, to understand the effects of the electric field. Our results indicate that electric fields keep particles suspended at higher elevations and enrich the concentration of larger particles at higher elevations. We extend our model from the small-scale system to long-range atmospheric dust transport to develop insights into the effects of electric fields on size distributions of lofted dust in the atmosphere. We show that the presence of electric fields and the resulting electrostatic force on charged particles can help explain the transport of unexpectedly large particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modeling results indicate that electrostatic forces may in some cases be relevant regarding the effect of atmospheric dust on the climate.

Two-year comparative study of snow cover dynamics and its impact factors on glacier surface

Snow cover on glacial surfaces is a sensitive environmental indicator. However, it is difficult to differentiate snow cover from a bare ice surface, and snow cover also changes rapidly during the melt season. Monitoring these dynamics requires sufficient time and spatial resolution; thus, traditional satellite data lack the necessary spatial resolution and rarely used to monitoring snow cover on glacier surface, which induced monitoring of snow dynamics on glacier is more challenging. Time-lapse photography has the advantage of obtaining images with high time and spatial resolution. By using an automated time-lapse digital camera, this paper documents two successive years snow cover dynamics on the Shiyi glacier and compared the meteorological conditions which induced different melt conditions. Monitoring indicate that the 2012 melt season experienced a higher snow cover fraction than the 2013 melt season because of a greater accumulated snow depth, lower air temperature and fewer sunlight hours. Successive photographs also indicate that, on the Shiyi glacier, atmospheric dust accelerates the snow melt speed and attenuates the snow depth. For the bare ice surface, the effects of atmospheric dust were reduced because the dusts were composed of Fine particles and are more easily washed away by melt water or rain. Studies on the Shiyi glacier indicate that the snow cover fraction is a key parameter that indicates the status of glacial accumulation or ablation.

Spectral effects of atmospheric dust and clouds on estimation of chlorophyll-a concentration from radiation measurements

Atmospheric dust and clouds modify the spectral distribution of the incident solar radiation. The influence of these spectral effects on the determination of chlorophyll-a concentration from the sea surface and remotely sensed radiation measurements made from ships, aircrafts or satellites was studied in the region off Northwest Africa in the Atlantic Ocean. The chlorophyll-a algorithms that are typically used in ocean colour community are based on ratios of reflectance values of different wavelengths. This fact, together with the wavelength dependent effect of atmospheric dust and clouds, causes uncertainties in the estimation of chlorophyll-a concentration. The most frequently used Morel, OC4v4 and OC3M chlorophyll-a algorithms were included in the investigation. The highest and the smallest uncertainties were found for the Morel and the OC3M algorithms, respectively. For the first time, sky conditions with dust and clouds together in the atmosphere were studied. Overestimations of the chlorophyll-a concentration of up to 8.8% were observed in the case of dusty skies without clouds. The concentration was also overestimated between 7.6% and 14.3% for skies with mixtures of dust and clouds increasing the solar irradiance. Underestimations of up to 24.1% and overestimations of up to 12.2% were found for skies with mixtures of dust and clouds decreasing the solar irradiance. Compensations of the influences of spectral effects were observed at special ratios of clouds to dust. Earlier results in relation to the impact of clouds on the estimation of chlorophyll-a concentration were verified. The spectral effects of cloudy skies cannot be neglected because it may result in an error of up to 40% of the estimated value.

Dust deposition pulses to the eastern subtropical North Atlantic gyre: Does ocean's biogeochemistry respond?

Enhancement of primary and export production following dust deposition pulses is well established for High Nutrient Low Chlorophyll regions, but the effect of atmospheric dust on the biogeochemistry of oligotrophic gyre regions remains unclear. Here we report atmospheric dust concentrations measured on Gran Canaria, Canary Islands, concomitantly with upper water biogeochemistry at the oligotrophic time series station ESTOC (European Station for Time series in the Ocean, Canary Islands) during a 2‐year period from winter 1997 to 1999. ESTOC is located in the eastern subtropical Atlantic gyre about 100 km north of Gran Canaria and 500 km west of the Sahara, and receives aeolian dust episodically mainly in winter and summer. We found a close correlation of the magnitude of atmospheric dust concentration in winter with the magnitude of downward particle flux at ESTOC, mainly due to a relative increase in lithogenic matter and carbonate sedimentation. Higher aerosol concentration was not accompanied by higher primary or export production, however, indicating that phytoplankton production remained unaffected by atmospheric nitrogen supply on a seasonal or yearly timescale. However, by estimating bioavailable iron input and the need of the phytoplankton population, we found that the highly episodic dust pulses might exert a feast and famine effect on the phytoplankton. Despite the high lithogenic matter input, carbonate, mainly stemming from coccolithophorids, exceeded in importance the role of lithogenic matter as ballasting agent of sinking organic matter.

A study of ultraviolet solar radiation at Cairo urban area, Egypt

Monthly mean daily values of global (G) and ultraviolet (UV) solar radiation incident upon a horizontal surface at Cairo urban area during two different periods (1969-1973 and 1993-1997) are presented, analyzed, and compared. The effect of urbanization processes on the solar radiation components is investigated and discussed. It was found that the total amount of the two radiation components, G and UV, received at the urban area of Cairo during the period 1969-1973 highly exceeds the total amount received during the period 1993-1997 for all months of the year. The mean relative reduction of G and UV reached 17.4% and 27.4%, respectively. A significant correlation between G and UV radiation has been found, and the recommended correlation equation has been stated to estimate the values of UV radiation which is difficult to measure at any site in the zone of Lower Egypt. Also, a comparative study of the two radiation components, G and UV, at urban (Cairo) and rural (Bahtim) areas during the period 1993-1997 revealed, that the urban area always has values of G and UV radiation distinctly lower than values found in rural area for all months of the year. Urban-rural mean reduction of G and UV reached 7.0% and 17.9%, respectively. The ratio of the ultraviolet to global radiation (UV/G) are calculated and compared with other sites in the Arabian Peninsula. The effect of atmospheric dust on the measured solar radiation components is also investigated and discussed.

A study of ultraviolet solar radiation at Cairo urban area, Egypt

The monthly mean values of global, G, and ultraviolet, UV, solar radiation incident on a horizontal surface at Cairo urban area during the two different periods (1969–1973) and (1993–1997) are presented, analyzed and compared. The effect of urbanization processes on the solar radiation components is investigated and discussed. It was found that the total radiation of the two components, G and UV received at the urban area of Cairo during the period (1969–1973) highly exceeds the radiation received during the period (1993–1997) for all months of the year. The mean relative reduction of G and UV reached 17.4% and 27.4% respectively. A significant correlation between G and UV radiation has been established and the recommended correlation equation has been stated to estimate the values of UV radiation that are difficult to measure at any site in the zone of Lower Egypt. Also, a comparative study of the two radiation components, G and UV, at urban (Cairo) and rural (Bahtim) areas during the period (1993–1997) revealed that the urban area always has values of G and UV radiation distinctly lower than that found in rural area for all months of the year. Urban–rural mean reduction of G and UV reached 7.0% and 17.9% respectively. The ratio of the ultraviolet to global radiation (UV/G) are calculated and compared with other sites in the Arabian Peninsula. The effect of atmospheric dust on the measured solar radiation components is also investigated and discussed.

Analysis and correlation of ultraviolet solar radiation from routine meteorological measurements over Egypt

For three years (1990-92) measurements of the monthly average daily global, G, and ultraviolet, UV, solar radiation incident on a horizontal surface at Cairo (30°15'N, 31°17'E) and Aswan (23°58'N, 32°47'E) are presented. processed and analysed. It was found that the computed monthly average daily values for the obtained solar radiation components, G and UV, were (18.1 MJ/m2, 0.55 MJ/m2, for Cairo and (22.1 MJ/m2, 0.71 MJ/m2, for Aswan. The effect of atmospheric dust on the measured solar radiation components is also investigated and discussed. The ratio of the ultraviolet to global radiation (UV/G) are calculated and compared with other sites in the Arabian Peninsula. A regression analysis has been done to find a correlation between G and UV at the selected sites during the three year period and the recommended correlation equations have also been stated.
 
 Since the meteorological measurements of UV solar radiation are not available over Egypt. except at Cairo (Lower Egypt) and Aswan (Upper Egypt) stations, our correlation equations can be used to calculate this component from the available global solar radiation measurements at any site in the two zones of Upper and Lower Egypt.

NICMOS Narrowband Infrared Photometry of TW Hydrae Association Stars

We have obtained 1.64, 1.90, and 2.15 μm narrowband images of five T Tauri stars in the TW Hya Association (TWA) using the Near-Infrared Camera and Multiobject Spectrometer aboard the Hubble Space Telescope. Most of the T Tauri stars in our study show evidence of absorption by H2O vapor in their atmospheres; in addition, the low-mass brown dwarf candidate, TWA 5B, is brighter at 1.9 μm than predicted by cool star models that include the effects of H2O vapor but neglect dust. We conclude that the effect of atmospheric dust on the opacity is important at 1.9 μm for TWA 5B, the coolest object in our sample. The available evidence suggests that the TWA is 5-15 Myr old. Comparison of the colors of TWA 5B with theoretical magnitudes as a function of age and mass then confirms previous claims that TWA 5B is substellar with a mass in the range 0.02-0.03 M☉. The accurate single-epoch astrometry of the relative positions and separation of TWA 5A and TWA 5B reported here should permit the direct measurement of the orbital motion of TWA 5B within only a few years.

The empirical relationship between global radiation and global ultraviolet (0.290–0.385) μm solar radiation components

Measurements of the monthly average daily global and global ultraviolet solar radiation over a period of three years (1985, 1986, 1987) in Kuwait are reported. Over the three years the computed yearly daily means for the above solar radiation components were 5.592 kW h/m 2 and 0.260 kW h/m 2. The effect of atmospheric dust on the measured solar radiation components is investigated. Employing the least-square linear regression analysis an estimated empirical function relating global radiation to ultraviolet radiation was proposed for the past three years' measurements.

Effects of dust on the heating of Mars' Surface and atmosphere

An analysis performed to determine the effect dust particles suspended in Mars' atmosphere have on the radiation reaching the surface both directly and scattered by the dust is described. Additionally, the fraction of incident sunlight directly absorbed by the atmospheric dust is computed. These calculations are done for ranges of dust opacity τ, incidence angle i, surface albedo as, and dust albedo ad, representative of the conditions on Mars. The effect of atmospheric dust on the Bond albedo is discussed. It is shown that direct heating of the atmosphere by dust absorption of solar radiation is adequate to explain Mars' south polar spring temperature inversion. Under most circumstances the presence of dust in Mars' atmosphere produces a lowering of the average surface temperature; this is probably the cause of the anomalously slow south polar cap retreat of 1977. Explicit forms for both the surface heating and the atmospheric heating as a function (τ, i, as, ad) are given.

Climatological effects of atmospheric particulate pollution

THE large amount of dust thrown into the atmosphere by volcanoes has long been recognised as an important factor in initiating climatic change that generally leads to cooler surface temperatures1–4. Another source of atmospheric dust is man's agricultural and industrial activity. It has been suggested that this anthropogenic source is a cause of cooling in a manner similar to that of volcanoes5,6. The primary mechanism thought to be responsible for cooling in both these situations is the backscatter to space of a portion of the incoming solar radiation. This reduction in heat input to the planet would cool its surface. Idso7–10 has argued for another effect of atmospheric dust—warming due to ‘thermal blanketing’. This mechanism would absorb some of the Earth's thermal radiation that would otherwise escape to space and then reradiate a portion of this radiation back to the surface, hence a rise in surface temperature with increasing atmospheric dust would be expected. We have completed an experiment recently in which the relative magnitudes of the solar and thermal radiation interactions with atmospheric dust were compared11. The results reported there indicate that there is a general climatological superiority for the thermal radiation interaction, predicting a net warming trend with increasing atmospheric dust for all but the most extreme cases of dust-loading of the atmosphere.

On some Observations made without a Dust Counter on the Hazing Effect of Atmospheric Dust

There was considerable difficulty in selecting a proper title for this paper. It may appear to some, after reading it, that a shorter and better title would have been, “On the Hazing Effects of Smoke.” But as smoke particles generally reflect a reddish-brown light, they do not therefore seem to be the cause of the whitish light which we call haze; and further, smoke particles generally condense into little masses of such a size that they fall to the ground before they are carried to any great distance. It was thought that as this paper is a continuation of previous work, and is founded on results already communicated to this Society, it would be better to keep to the use of the same terms, and as usual, under the name of “dust particles,” to include all the solid and liquid products of combustion, of whatever size or colour they may be.